This invention relates to a wet scrubbing apparatus and more particularly relates to a damper assembly disposed within a wet scrubbing device for regulating the rate of flow-through gases to be scrubbed through individually and separately operative contactor beds.
With the growing concern about the quantity of sulfur oxides, particularly sulfur dioxide, being introduced into the atmosphere from industrial stack gases, emphasis has focused upon developing air pollution control systems, particularly wet scrubbing systems, that are capable of achieving a high degree of sulfur dioxide removal from such industrial stack gases. One advantageous type of system that has been proposed is a wet scrubbing system including a scrubbing tower with a packing therein composed of light weight spheres adapted to form a unitary circulating bed in which the spheres are in contact with one another yet maintain a limited freedom of movement relative to one another. The bed as a total unit is designed to circulate through the scrubbing tower. To assist this circulatory movement the spheres are guided by a slanted retaining grid or plate located in the upper region of the tower. While the circulating bed, like certain conventional packing, provides a large interfacial area of contact between the liquid descending through the interstices between the spheres and the gases ascending in countercurrent flow to the liquid, it has advantages over other more conventional systems. One such advantage is that due to the rotational and circulatory movement of the balls in the bed no channeling occurs. Solid particles carried by the liquid or gas do not settle permanently on the packing, but on the contrary may be continuously washed off. Plugging is thereby reduced and there is no need for periodic shut down to clean or replace the packing.
In this type of scrubber maintenance of the desired type of motion of the gas contact elements depends upon the fluid velocities, and particularly on the velocity of the incoming dirty gas. With very low gas velocities there is not sufficient lift for the gas contact elements to be buoyed off a bottom restraining grid and to circulate in the manner contemplated. This is particularly true where the densities of the elements are high and where the rate of liquid flow in the opposite direction to that of the gas flow is relatively high. On the other hand, when the gas velocities are too high, there is a problem of lodging some or all of the gas contact elements against the restraining grids. Specifically, the gas and liquid velocities used in a circulating scrubber of the type contemplated are generally in the range of about 500 to 1700 feet per minute and 10 to 75 U.S. gallons per minute per square foot, respectively. As a result of such high velocities, not only is throughput or capacity of the apparatus considerably increased but also absorption efficiency is markedly improved. Also, recovery of the gas constituents is improved, which may be the purpose of the operation.